The light at the end of the tunnel

Most cement and mining companies have several material transportation systems that rely on conveyor belts inside underground tunnels. This approach has been utilised for many years and is practical and economical. The amount of material storage above the tunnel is very large and easy to evacuate with discharge chutes underneath the stockpile.

A typical underground tunnel has several discharges in a straight line that are regulated to feed the material onto the conveyor belt at a controlled rate. The fed material has a large particle distribution range, from microns to centimetres. The varying particle sizes hitting the belt generate a significant amount of dust, which becomes airborne. This results in a challenging and dusty environment for operators working within the tunnel.

One answer

One widely adopted solution involves installing a large dust collector at one end of the tunnel. This setup includes a long horizontal duct that runs along the tunnel’s ceiling, branching out to each individual discharge chute where a canopy is installed. To maintain a high velocity of airflow within the duct and prevent dust from settling, the duct’s diameter is intentionally sized smaller than what is typically recommended for standard velocity.

This approach presents sustainability challenges. When the dust collector is turned off, dust settles within the duct. Once the collector is turned back on, the system struggles to lift and remove the settled dust. This inefficiency can lead to operational disruptions and increased maintenance requirements, highlighting the need for a more effective dust management strategy in such environments.

Shortly after its initial installation, often within a matter of weeks, the main duct begins to experience a reduction in suction power due to the dust accumulation. This decrease in efficiency is a direct consequence of dust settling within the ductwork. This in turn hampers the system’s ability to effectively remove airborne particles from the environment.

Another answer

To mitigate the dust accumulation issue, the main duct is sometimes designed in modular sections, featuring flanges at both ends or equipped with small access windows at the bottom. These design choices are intended to facilitate the removal of settled dust. However, this approach requires significant labour and often fails to achieve the desired outcomes. The labour-intensive nature of this solution, coupled with its limited effectiveness, frequently leads to the plant abandoning this method of dust removal. The continuous challenge of managing dust accumulation in such systems underscores the need for more efficient and less labour-intensive solutions.

The diminished suction from inadequate ventilation exacerbates the working conditions within the tunnel, leading to a challenging environment for the personnel. Continuous efforts to clean walkways and enclosures become a recurring issue, presenting constant headaches for the maintenance and operations teams. This situation highlights the critical need for more effective dust management and ventilation strategies to ensure a safer and more conducive working environment.

The right answer

Among the solutions available to combat the challenges of a dusty environment in such settings, the horizontal pulse jet dust collector stands out as an effective and proven system. This technology utilises a combination of air pulsing and filtration to continuously clean the filter media, ensuring that dust particles are efficiently captured and removed from the air stream.

The horizontal orientation of these systems offers advantages in terms of ease of installation, maintenance, and overall effectiveness in maintaining cleaner air within the work environment, significantly improving the conditions for those operating within these challenging settings.

Additionally, the installation of a correctly sized horizontal pulse jet dust collector adjacent to each discharge chute feeding the conveyor belt can significantly improve dust control by creating a consistent negative pressure area between the bottom of the dust collector and the conveyor belt. This negative pressure effectively captures airborne dust particles, preventing them from escaping into the surrounding atmosphere. When the pulse jet system activates to clean the filters, the dislodged dust falls directly onto the conveyor belt, where it can be evacuated along with the transported material. No additional material handling equipment is required.

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